This invention relates to a method of making large scale integrated circuits, e.g., charge coupled devices (hereinafter referred to as CCD's) and, more particularly, to a method of making CCD's used as imaging arrays.
CCD arrays are very large scale integrated circuits that have come to be used as imagers in television cameras. These imagers include a photosensing register, often referred to as an A register, a temporary storage register, often referred to as a B register and an output register, often referred to as a C register. The A and B registers are generally identical and each includes a plurality of channels, each having a plurality of stages, formed adjacent one surface of a semiconductor body. The C register has a number of stages equal to the number of channels in the A and B registers and outputs to a transistor amplifier. As is usual, the channels are separated by channel stops and excess charge drains as should be understood by those skilled in the art. Over the registers there is formed an oxide layer and over this layer, control electrodes that control the storage and transfer of charge along the channels.
In use, the B and C registers are usually masked against light and the A register is associated with a lens that focuses light thereon. Light from an image generates photocharge in the A register which is accumulated in the channels, then transferred to the B register whereupon photogeneration can then reoccur in the A register. The charge in the B register is transferred into the C register one line at a time from where it is read serially by the output transistor amplifier.
One problem with the images displayed from these devices is the presence of white spots and lines. These spots and lines, of course, detract from the quality of the picture.